Impression control apparatus employing two sets of stops



y 1966 w. A. HEIDT ETAL 3,259,223

IMPRESSION CONTROL APPARATUS EMPLOYING TWO SETS OF STOPS Filed Sept. 21, 1964 2 Sheets-Sheet 1 INVENTORS. WILLIAM A. HEIDT NEIL D. WALTON VATTORNEY.

y 5, 1966 w. A. HEIDT ETAL 3,

IMPRESSION CONTROL APPARATUS EMPLOYING TWO SETS OF STOPS Filed Sept. 21, 1964 2 Sheets-Sheet 2 FIG. 3

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IMPRESSION SETTING IMPRESSION SETTING United States Patent 3,259,223 IMPRESSION CONTROL APPARATUS EMPLOY- IN G TWO SETS 0F STOPS William A. Heidt and Neil D. Walton, Lexington, Ky.,

assignors to International Business Machines Corporation, New York, N.Y., a corporation of New York Filed Sept. 21, 1964, Ser. No. 397,701 9 Claims. (Cl. 197-17) The present invention relates generally to apparatus for accurately controlling the printing impressions of the type of power driven business machines, such as typewriters.

In the typewriter art, it is well known to provide a plurality of type bar drive mechanisms that may be individually connected with a continuously rotating power roll to drive the selected type bars toward the printing platen. When the typist depresses a character keylever, a member, such as a serrated cam, is caused to engage the power roll. The cam is driven about its pivotal mounting to drive the associated type bar from its rest position toward the printing platen and cause printing of the selected character.

The density of the printed character will depend in part on the driving force imparted to the type 'bar drive mechanism. This in turn depends on the length of time the cam is :operatively connected with the power roll. It is known to provide abutment means for disconnecting the cam from the power roll after a predetermined time interval and this abutment means may take the form of an adjustable knock off element. By proper adjustment of the individual knock off elements, it is possible for a type bar mechanism associated with a character having a relatively large surface area, like the upper case W, to be driven longer and consequently with more force than the type bar mechanism associated with a character having a relatively small surface area, like the period.

Many present day typewriters are provided with means for varying the printing impressions of type in accordance with the kind of printing being accomplished, such as the number of copies being typed with the use of carbon paper. For example, in the Model C electric typewriter manufactured and sold by international Business Machines Corporation, Armonk, New York, a typist settable impression control lever is provided that causes movement of all of the knock off or stop elements en banc when actuated to Vary the printing impressions of the type. The printing impressions of the type may be varied individually or as a group by adjusting the individual knock ofl? or stop elements or moving the impression control lever, respectively. These arrangements are fully disclosed on pages 10 19 of the IBM Customer Engineering Instruction Mai1ualStandard Type-writer Model C-l, copyright 1960 and published by the above organization which is made of record for those desiring more information concerning the same.

While type bar drive mechanisms of the character described above have been Widely employed and provide printing of excellent quality, it has :been found that when the impression control lever is at -a setting which produces printing having a high average density, such as when making a large number of carbon copies, there is a tendency for those characters with relatively small surface areas to emboss or even cut the original and initial copies. This tendency is particularly pronounced with the period and other similar punctuation characters. Embosing or cutting detracts from the over-all quality of the printed material and is to be avoided whenever possible.

Briefly, the present invention is concerned with means for limiting the maximum force with which at least some 3,259,223 Patented July 5, 1966 of the type bar drive mechanisms of a typewriter are driven toward the printing platen and the resultant densities of printing of the associated characters while permitting the densities of printing of other characters to be further increased. It has been determined experimental 1y that the densities of certain printed characters increase more rapidly than the densities of other characters as the impression control lever is adjusted. The character whose densities increase more rapidly may emboss or even severly cut the paper at impression settings. In order to compensate for this condition, an additional or second group of adjust-able abutment or stop means is provided. Each abutment means may comprise an adjustable knock off or stop element which is relatively station-arily mounted with respect to the frame of the typewriter. It is the function of the second group of knock off or stop elements to limit the maximum density of printing of individual characters at any desired optimum setting without interfering with the adjustment of the densities of printing of other characters.

It is the primary or ultimate object of this invention to provide highly improved impression control apparatus which is effective to eliminate embossing or cutting of the material being printed by a typewriter or similar business machine at high settings of the apparatus. This provides printing of improved over-all quality having a more uniform appearance.

Another object of the invention is the provision of impression control apparatus for limiting the maximum densities of printing of at least some of the characters while yet permitting further increases in the densities of printing of at least some of the other of the characters. Two rows of knock off or stop elements which are relatively movable with respect to each other are provided and the knock off or stop elements in one of the rows define the maximum densities of printing of the associated characters.

A further object of the invention is to provide impression control apparatus of the type outlined above which is characterized by its extreme simplicity in construction and operation. The apparatus involves a minimum of change in the design of present type bar drive mechanisms and is capable of long periods of sustained operation without maintenance or adjustment.

The fore-going and other objects, features and advantages of the present invention will be apparent from the following more particular description of a preferred embodiment of the invention, as illustrated in the accompanying drawings.

In the drawings:

FIGURE 1 is a side elevation of a type bar drive mechanism in the at rest or unoperated condition embodying impression control apparatus constructed and operated in accordance with the teachings of this invention;

FIGURE 2 is a side elevation similar to FIGURE 1' but showing the type bar drive mechanism in the operated condition;

FIGURE 3 is a fragmentary side perspective View showing particularly the mounting of the two rows of knock olf or stop elements; and

FIGURES 4 and 5 are graphs representing observed densities versus diiferent settings of the impression control apparatus for various characters which are useful in explaining the utility and operation of the apparatus disclosed.

Referring now to the drawings, the reference numeral 10 designates a power roll which is continuously driven by motor means, not shown, in the direction of arrow 11.

The power roll has a resilient outer surface and is pro vided to drive various instrumentalities of the typewriter that are adapted to be intermittently connected thereto as will be hereinafter further explained. For the type bar drive mechanism shown, a character keylever 14 is pivotally mounted at its rear end by rod 15. The keylever 14 is normally urged upward against stop 16 by a spring 17 extending from the front end of the keylever 14 to a stationary guide comb 18. Intermediate the ends of the keylever 14 is a projecting tab portion 19 which carries a properly inscribed key cap 20.

Disposed between the character keylever 14 and the power roll is a cam lever assembly that is generally designated by the reference numeral 22. The cam lever assembly comprises a cam 23, a cam lever 24 and a trip lever 25. The cam 23 is generally L-shaped and its shorter leg portion 26 is formed with teeth 27 which are adapted to firmly engage the resilient outer surface of the power roll 10 when the type bar drive mechanism is actuated. The cam 23 is pivotally mounted by a shouldered rivet 29 to the cam lever 24. The cam is biased clockwise toward its rest position by a cam spring 30.

The earn lever 24 is mounted for pivotal movement about stationary pivot rod 31. Attached to the upwardly projecting and elongated arm of the cam lever 24 is a type bar link 32 which connects with the lower end of type bar 33. The type bar 33 mounts type slug 34, is pivoted by type bar fulcrum 35 and normally engages type bar rest 36. The type bar 33, type bar link 32 and cam lever 24 are biased toward the rest position by the cam lever spring 37.

The trip lever is mounted to the cam lever 24 by a shouldered rivet 40 which extends through an elongated aperture 41 in the trip lever. This aperture allows the trip lever 25 to slide forward and back on rivet 40 as well as rotate about it. A spring 42 extending from the trip lever 25 back to the cam lever 24 holds the trip lever 25 up and to the rear in its rest position as shown in FIG- URE 1 of the drawings. The trip lever 25 has two lugs 43 and 44 formed on opposite sides thereof. The upper lug 43 is positioned directly under a lug 47 on the character keylever 14 while the lug 44 overlies the longer leg portion 28 of cam 23.

In the operation of the apparatus so far described, the typist depresses the character keylever 14 to pivot the same downwardly about rod 15. The lug 47 on the bottom of the keylever engages the top lug 43 on the trip lever 25. The trip lever 25 pivots downwardly about rivet 40 and causes the cam 23 to rotate counterclockwise until the teeth 27 engage the resilient outer surface 11 of the continuously rotating power roll 10. The distance between the lower end of the teeth 27 on the cam 23 and the rivet 29 is greater than the distance from the upper end of the teeth 27 on the cam 23 and the rivet 29. This rise or eccentricity of the cam forces the cam lever assembly 22 to pivot counterclockwise about pivot rod 31. The cam lever 24 pulls on the type bar link 32 to drive the type bar 33 and the type slug 34 toward a printing platen 48 as is shown in FIGURE 2 of the drawings.

Type impression or density of the printed character is controlled by the length of time the cam 23 is allowed to engage and be driven by the power roll 10. The farther the cam 23 drives the type bar 33 and type slug 34 toward the printing platen 48, the heavier and more dense the impression of the type. To control the density, a plurality of cam knock off or stop fingers 50 are mounted on and carried by a cam knock off bar or stop member 51. The knock off bar 51 extends across the width of the typewriter beneath the aligned cam lever assemblies 22 as is shown in FIGURE 3 of the drawings and a knock otf or stop finger 50 is provided for each cam lever assembly. Threadably received in the cam knock off bar 51 under the free ends of the knock oflf fingers 50 are a plurality of transversely aligned adjusting screws 53. One of the adjusting screws 53 is associated with each cam lever assembly 22. Each of the knock off fingers 50 is adapted to be engaged by the extreme end of the longer leg portion 28 of an associated cam 23 as the cam is rotated by the power roll 10 in response to depression of the associated character keylever. Before the type slug 34 reaches the printing platen 48, the end of the cam 23 meets the cam knock off finger 50 to stop the rotation of the cam.

The momentum of the apparatus causes the type bar 33 and type slug 34 to continue their movement toward the printing platen 48 to effect printing. The continued motion of the cam lever 24 releases the cam 23 from the power roll 10 and cam spring 30 restores the cam 23 to its rest position against the cam lever 24. By adjusting any of the screws 53, the density of the impression of the associated character is changed since the length of time the cam is drivingly connected to the power roll is varied and the type bar is driven a difierent distance toward the printing platen.

The knock off bar or stop member 51 is pivotally mounted at its forward end by pivot pins 56 to the frame of the typewriter. Springs 57 at the rear of the knock off bar cause it to be held down against an eccentric impression control shaft 58. Mounted on one end of the impression control shaft 58 is a lever 59 which is interconnected by a link 60 to a typist actuatable impression control lever 61. Moving the impression control lever 61 rotates the eccentric impression control shaft 58 to raise or lower the knock off bar 51. Raising the knock off bar 51 decreases the densities of impression of all printed characters while lowering the knock off bar increases the densities of impression of all printed characters. Reference indicia 62 on the impression control lever 61 form a scale to provide the typist with a reference for the various impression settings.

Located between the knock off bar 51 and the power roll 10 is a secondary knock off bar or stop member 63 having a clevis shaped end portion that nestingly receives the pivot rod 3-1. Threadably mounted in the secondary knock off bar 63 are a plurality of transversely aligned adjustable knock off stops or screws 64. Each of the knock off screws 64 is associated with one of the cam lever assemblies 22. The knock off screws 64, while being individually adjustable, are relatively stationarily mounted with respect to the frame of the typewriter. As will be hereinafter more fully explained, it is the function of each adjustable knock off screw 64 to engage the longer portion 28 of the associated cam 23 and terminate the driving connection of the cam with the power roll at a selected setting of the impression control lever. This effectively defines and provides a maximum density of impression for the associated character even though the densities of the impressions of other characters can be increased *by moving the impression control lever 61 to higher settings.

Referring now to FIGURES 4 and 5 of the drawings, there are shown two graphs which depict the densities observed for various characters at different settings of the impression control lever 61. The numerals along the horizontal axes of the curves correspondto the indicia on the impression control lever forming the scale 62.

In FIGURE 4, representative density curves for the printing produced by three different characters of a typewriter not equipped with the secondary knock off means of the present invention are shown. The typewriter does not include the knock off stops or screws 64 and the adjustment screws '53 are set so that printing of a desired density when typing only the original is provided at a setting of five of the impression control lever. The character represented by density curve 70 has a relatively large surface area whilethose represented by curves 71 and 72 have intermediate and relatively small surface areas, respectively. The smaller the area of the character, the faster the density of the printing increases as the impression control setting is raised. The characters represented by the curves 71 and 72 are more likely to emboss or cut the material being printed than the character represented by cruve 70 at the higher impression settings.

FIGURE 5 shows the observed density versus different settings of the impression control lever curve 73 for a character in a typewriter having the secondary knock ofl. means of this invention. The knock ofi screw 64 associated with this character has been adjusted so that it engages the longer leg portion 28 of cam 23 when an impression setting of five is reached. The cam 23 is disengaged from the power roll after it has been driven the same distance by the knock off screw 64 at all settings of the impression control lever 61 from five to ten. The density of the printing of the character increases in the normal manner as the impression control lever setting is increased from zero to five but the density remains constant as represented by horizontal portion 74 of curve 73 as the impression control lever setting is moved from five to ten.

It should be understood that the maximum density of impression of a character can be selected or varied as desired by adjusting the associated knock off screw 64. For example, if the knock off screw 64 corresponding to the character represented by curve 73 were adjusted so that maximum density is reached at impression settings of either three or seven, then the curve would follow dotted lines 75 or 76, respectively. The settings of the individual secondary knock off screws 64 will depend on the particular characters involved and the results desired. As a general practice, the secondary knock off screw 64 ascociated with a character which has a relatively small surface area is adjusted so the printing of the character will reach its maximum density at a lower setting of the impression control lever than the printing of a character having a larger surface area.

It should now be apparent that the objects initially set forth have been accomplished. Of particular importance is the fact the apparatus disclosed is extremely useful in preventing embossing and cutting of the material being printed by the characters having small surface areas, such as the period and other similar punctuation marks, while yet retaining the ability to adjust the over-all density of the printing through a wide range as required for various printing operations. It is possible to provide secondary knock otf stops or screws for each of the cam lever assemblies or for only a portion of the cam lever assemblies. In certain typewriters, different knock off means are employed for upper and lower case characters and it is within the scope of the present invention to provide each of the upper and lower case knock off means with secondary knock off means. Also, while the secondary knock off means comprises elements which are stationarily mounted with respect to the typewriter frame and do not move when the impression control lever is adjusted in the disclosed embodiment of the invention, the secondary knock off means can be mounted for movement in response to adjustment of the impression control lever to obtain highly complicated density versus impression setting functions for at least a portion of the characters.

While the invention has been particularly shown and described with reference to a preferred embodiment thereof, it will be understood by those skilled in the art that the foregoing and other changes in form and details may be made therein without departing from the spirit and scope of the invention.

What is claimed is:

1. A power driven typewriter having a plurality of type elements;

a continuously rotating power roll;

a plurality of rockable cams associated with said type elements; keyboard means responsive to operator actuation operative to move a rockable cam corresponding to a selected character into driven relation with said power roll to impart a driving force to the associated type element;

means to disengage said rockable cams from said power roll to limit the driving forces imparted to said type elements;

said means to disengage comprising a first stop member having a first group of stops thereon;

' a second stop member having a second group of stops thereon; operator controlled means mounting said first and second groups of stops for relative movement of said first and second groups with respect to each other through a range of movement; said second stop group being operative to disengage said rockable cams during the latter portion of said range of movement; and said second stop group defining means for limiting the maximum driving forces imparted to at least a portion of the type elements while permitting further adjustment in the driving forces imparted to other type elements. 2. A business machine having a plurality of type elements;

a plurality of rockable members selectively operable to drive an associated type element to printing position;

impression control apparatus comprising a first stop member having a plurality of first stops mounted thereon; each of said first stops being associated with one of said rockable members and operative to regulate the driving force imparted to an associated type element by said one of said rockable members; means mounting said first stop member for movement to simultaneously alter the driving forces imparted to said type elements when said rockable members are selectively operated; a second stop member having a plurality of second stops mounted thereon;

each of said second stops being associated with one of said rockable mentbers;

said second stop member being relatively stationarily mounted with respect to said business machine; and each of said second stops being associated with one of driving force imparted to an associated type element by one of said rockable members when said first stop member is moved to a predetermined position.

3. Apparatus according to claim 2 further characterized by:

each of said first and second stops being adjustably mounted on said first and second members to provide a means for individually adjusting the driving force imparted to a type element by one of said rockable members.

. 4. Apparatus according to claim 2 further characterized b said rockable members being aligned in side-by-side relation with respect to ,each other in said business machine;

said first and second stop members extending beneath said rockablemembers in generally transverse relation with respect to said aligned rockable members; and

said stop members being aligned in side-by-side relation with respect to each other.

5. Apparatus according to claim 2 further characterized said means mounting said first stop member comprises a cam member engaging said first stop member; and

operator settable means for determining the position of said cam to move said first stop member.

6. A business machine having a plurality of type elements;

a plurality of movable members selectively operable to drive an associated type element to printing positions;

impression control apparatus comprising a first stop member having a first group of stops mounted thereon;

each of said first stops being associated with one of said movable members and operative to regulate the driving force imparted to an associated type element by said one of said movable members; a second stop member having a second group of stop mounted thereon; each of said second stops being associated with one of said movable members and operative to regulate the driving force imparted to an associated type element by one of said movable members; operator controlled means mounting said first and second groups of stops'for relative movement of said first and second groups with respect to each other through a range of movement; and the first and second stops associated with a particular movable element being operative to regulate the driving force imparted to an associated type element during ditferent portions of said range of movement. 7. Apparatus according to claim 6 further characterized by:

a continuously rotating power member; said movable members each being adapted to be drivingly connected with said rotating power member when the associated character is selected for printing; and said first and second stop groups being operative to terminate the driving connections between said movable members and said rotating power member. 8. A business machine having a plurality of type elements;

type selection means operative to bring a selected type element to a printing position; impression control apparatus for controlling densities of printing impressions formed by said type elements; said impression control apparatus comprising first and second stops for regulating the printing force imparted to at least one of said type elements; means mounting said first and second stops for relative movement with respect to each other through a range of movement; said first and second stops being operative to regulate the printing force imparted to at least one of said type elements during different portions of said range of movement; said means mounting comprising means for moving said first stop through said range of movement; said second stop being stationarily mounted with respect to said business machine; said second stop being operative during the latter portion of said range of movement; and said second stop providing a means to limit the maximum printing force imparted to at least one of said type elements while permitting movement of said first stop during said latter portion of said range of movement. 9. A power driven typewriter having a plurality of type elements;

a continuously rotating power roll;

a plurality of rockable cams associated with said type elements;

said rockable cams being arranged in generally side-byside relation with respect to each other in said typewriter;

keyboard means responsive to operator actuation operative to move a rockable cam corresponding to a selected character into driven relation with said power roll to impart a driving force to the associated type element;

means to disengage said rockable cams from said power roll to limit the driving forces imparted to said type elements and for controlling densities of printing impressions for-med by said type elements;

said means to disengage comprising first and second stop members having a plurality of first and second stops thereon, respectively;

means mounting said first and second stop members in aligned side-by-side relation below and transversely of said rockable cams for relative movement with respect to each other through a range of movement;

the first and second stops associated with at least one of said rockable cams being operative to regulate the printing force imparted to the associated one of said type elements during diflerent portions of said range of movement;

said means mounting comprising operator controlled means for moving said first stop member through said range of movement;

said second stop member being relatively stationarily mounted with respect to said typewriter;

said second stops being operative during the latter portion of said range of movement; and

said second stops providing a means to limit the maximum force imparted to at least one said type element while permitting movement of said first stop member mounting said first stops during said latter portion of said range of movement.

References Cited by the Examiner UNITED STATES PATENTS 1,818,200 8/1931 Dorsey 197-17 2,750,022 6/1956 Long 197-17 2,796,966 6/1957 Toeppen 19717 References Cited by the Applicant UNITED STATES PATENTS 2,717,685 9/1955 Buhler. 2,750,022 6/ 1956 Long. 2,907,436 10/1959 Frechette.

ROBERT E. PULFREY, Primary Examiner.

55 EDGAR S. BURR, Assistant Examiner. 

1. A POWER DRIVEN TYPEWRITER HAVING A PLURALITY OF TYPE ELEMENTS; A CONTINUOUSLY ROTATING POWER ROLL; A PLURALITY OF ROCKABLE CAMS ASSOCIATED WITH SAID TYPE ELEMENTS; KEYBOARD MEANS RESPONSIVE TO OPERATOR ACTUATION OPERATIVE TO MOVE A ROCKABLE CAM CORRESPONDING TO A SELECTED CHARACTER INTO DRIVEN RELATION WITH SAID POWER ROLL TO IMPART A DRIVING FORCE TO THE ASSOCIATED TYPE ELEMENT; MEANS TO DISENGAGE SAID ROCKABLE CAMS FROM SAID POWER ROLL TO LIMIT THE DRIVING FORCES IMPARTED TO SAID TYPE ELEMENTS; SAID MEANS TO DISENGAGE COMPRISING A FIRST STOP MEMBER HAVING A FIRST GROUP OF STOPS THEREON; A SECOND STOP MEMBER HAVING A SECOND GROUP OF STOPS THEREON; OPERATOR CONTROLLED MEANS MOUNTING SAID FIRST AND SECOND GROUPS OF STOPS FOR RELATIVE MOVEMENT OF SAID FIRST AND SECOND GROUPS WITH RESPECT TO EACH OTHER THROUGH A RANGE OF MOVEMENT; 